Reflector for automobile headlights



Dec. 3, 1929. 1.. c. LAURENT 1,738,304

REFLECTOR FOR AUTOMOBILE HEADLIGHTS Filed July 20, 1926 Louis CLaurwf.

alike: 1x94 Patented Dec. 3, 1929 a Louis 0. LAURENT, or nnnvnn, ooonnno REFLECTOR IOR AUTOMOBILE HEADLIGHTS Application filed July 20,

This invention relates to improvements in reflectors for automobileheadlights.

It is well known to all who have occasion to drive automobiles afterdark that the glare E from the headlights of approaching automobiles ismost annoying and it is easy to imderstand how serious accidents oftenoccur from this cause. a

I have found from a series of experiments to that, with the usual formof paraboloijdal reflectors, now almost universally used, the greaterpart of the objectionable glare comes from the central portion of thereflector which therefore, instead of being of service in pro ducinguseful illumination is actually highly objectionable.

It is the object of this invention to produce a reflector which shall beso constructed that the central glare emitting portion will not refleetharmful rays but will rather assist in producing useful roadillumination.

The ordinary reflector is so constructed that a section taken on anyplane passing through the axis is a parabola. One of the properties of aparabolic reflector is that all rays of light which enter it parallelwith its axis will be reflected so as to intersect each. other at apoint located on the axis, which point is known as the focal point ofthe pa rabola. Conversely, light originating at the focal point will bereflected as a cylindrical beam parallel with the axis of the parabola.As an automobile headlight reflector is only about eight inches indiameter, it is evident that satisfactory road illumination cannot beobtained with the source of light at the focal point. It is thereforethe usual practice to adjust the lamp to such a position that thefilament lies either to the front or to the rear of the focal point asit is thereby possible to obtain any desired dispersion of the light. Ifthe source of light is to the front of the focal point, the reflectedrays will emerge from the reflector a cone whose apex lies to the frontand this is known as a convergent ray adjustment. If the light isbetween the focal point and the reflector, the light will issue as acone whose apex lies to the rear of the reflector. This is termed adivergent ray adjustment. With the light at the focal point,

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1926. Serial No. 123,632.

there will be no reflected rays that will cause a blinding glare toanyone outside of the narrow cylindrical beam but as soon as the lightis moved away from the focal point, glare points will develop especiallyat that part of the reflector immediately surrounding the arms. 7 i

It is the object of this invention to so modify the construction of thereflector that all possibility of glare from the central part of thereflector will be eliminated and at the same time all of the lightgenerated by the amp utilized.

The above and other objects which will become apparent as thedescription proceeds are attained by means of a construction which Iwill nowdescribe in detail, reference for this purpose being had to theaccompanying draw-- ing in j which the invention has been illustratedand in which:

Fig. l is a plan view showing the. distribution of light from a pairofspaced headlight lamps provided with my improved reflectors;

Fig. 2 is a section of one of the reflectors. taken on an axial planeand showing the posi tion of the source of light and the path of therays;

Fig. 3 is a front elevation of one of the re flectors and shows theappearance of the reflector with the lamp lighted; and

Fig. 4 is a side elevation showing the vertical distribution of thelight.

In the drawings R and L (Fig. 1) repre sent respectively the right andleft headlights of an automobile which are equipped with my improvedreflectors. In the drawing these headlights have been so arranged thattheir axes converge. The lines 0, X and O X l'cpresentthe axesrespectively of the reflectors R and L. The arrangement shown in 1 mayor may not be followed as it is possible tohave the axes ofthereflectors parallel and still obtain good results but in the experimentsca rried out by applicant, the best results were obtained withconvergent axes.

As the invention resides in the reflector, I willnow proceed to describethe same and for this purpose reference will now behad more particularlyto Fig. 2 in which oneof the reflectorshave been shown in section.

The line 0, X represents the axis of the parabola with respect to whichthe reflecting surface is symmetrical. That portion of the reflectorforming the zone P bounded by planes 2 and 3 has circularcross sectionsin planes perpendicular to the axis 0, X and parabolic crosssections inplanes passing through the axis. 7

The point Flies on the axis 0, X and is the focal point of thereflector. If a concentrated source of light is located at F the rays oflight which impinge on the reflecting surface between planes 2 and 3will be reflected in a direction parallel to the axis. One such ray isindicated by F. 3. 4. That portion of the reflector between the axis andthe locus of the intersection of the reflector with plane 2 2, insteadof following the dotted lines so as to complete the parabola, is madeinto i a truncated cone whose base is formed by the plane 2 and whosetop is formed by plane 5. The apex of the cone lies at the focal pointF.

It is now evident that rays of light that originate at F cannot impingeon the conical surface but are projected parallel with it and impinge onthe parabolic surface P.

It has been explained above, that satisfactory road illumination cannotbe obtained with the source of light at the focal point and it istherefore necessary to adjust the lamp to such a position that thefilament lies to the front of the focal point. In order to illustratethe path of the light with the lamp in one operative position, I haveindicated the filamentat point 8. Rays of light 8, 9 and 8,3 impinge onthe parabolic reflectlng surface and are reflected as rays 9, 10 and 3,11

which converge and cross at 12 (Fig. 1).

Rays 8, 13 strike the conical reflecting surface at 13 and are reflectedalong lines 13, 14 to the reflecting surface P from which they arereflected along lines 14, 15, which, in

the example shown, are slightly divergent. It is evident that the anglesat which the light emerges can be varied slightlyby moving the lampalong the axis but as long as the source of light is to the front of thefocal point F the greater part of the light will emerge as convergentrays while that part that strikes the conical surface 7 .will emerge asdivergent or parallel rays, depending upon the position of the lightsource 8.

As'no light rays will be reflected outwardly 5 from the cone '7, thelatter will appear as a dark ring like that shown in'Fig. 3.

' By properly adjusting the light source 8, a good illumination can beobtained on the road surface without any objectionable glare. i

It is, evident that if the source of light is moved: to the rear of thefocal point F a wholly different distribution of the light will takeplace as the rays that strike the parabolic surface P will then bereflected as a divergent cone If the source of light is moved far enoughto the rear of plane 5, no light will strike the inner surface of thereflector.

From the above it will be apparent that I have produced a reflector ofsimple construction in which no glare can come from the portionimmediately surrounding the axis, and which therefore makes it possibleto produce good road illumination without causing inconvenience todrivers of cars that travel in the opposite direction.

Having now described the invention, what is claimed as new is:

1. A headlight comprising a reflector having a continuous reflectingsurface consisting of a parabolic zone and a forwardly projectingtruncated cone whose axis coincides with the axis of the parabolicreflector and whose vertex coincides with the focal point of the latter,and a source of light located within the reflector in front of the focalpoint.

2. A headlight comprising a reflector having a reflecting surfaceconsisting of a parabolic zone and a substantially conical truncatedsurface whose axis coincides with the axis of the parabolic surface andwhose vertex lies substantially at the focal point of the parabolicreflector, and a lamp within the reflector with its source of light onthe optical axis and in front of the focal point thereof.

In testimony whereof I afiix my signature.

LOUIS C. LAURENT.

